An apparition appearing in the Konjaku Gazu Zoku Hyakki, in the form of a flaming wheel with a bald monk's face in the center. Sekien writes:

車の轂に大なる入道の首つきたるが、かた輪にてをのれとめぐりありくあり。
これをみる者魂を失ふ。 「此所勝母の里」　と紙にかきて、家の出入の戸におせば、
あへてちがづく事なしとぞ。
On the hub of a wheel there is a great monk's head, and riding on the single wheel it goes around and around.
A person who sees it will lose their soul. If you write "here is the home of a winning mother" on a piece of paper,
and apply it to the door where you come and go from the house, [the wanyūdō] will not dare approach.

The charm invoking the "home of a winning mother" apparently refers to a story in the Records of the Grand Historian concerning Confucius' pupil Zēngzǐ, known for his filial piety. Disgusted at having a reputation of "winning for his mother," Zēngzǐ could not set foot in the home of a "winning mother". How exactly this is related to the wanyūdō is unclear.

The shape of the wanyūdō itself seems to be based on an image from the Shokoku Hyaku Monogatari 諸国百物語, a ghost story collection published in 1677. Titled "Katawa-guruma Phenomenon of East Tōin in the Capital'' 京東洞院かたわ車, this drawing depicts a wheel-like being seen on a street in Kyoto.


Citations
1. Murakami 2005 p. 358.
2. Inada p. 136